A computer network is a collection of interconnected computing devices that exchange data and share resources. In a packet-based network the computing devices communicate data by dividing the data into small blocks called packets. Certain devices within the network, such as routers, maintain routing information that describes routes through the network. In this way, the packets may be individually routed across the network from a source device to a destination device. The destination device extracts the data from the packets and assembles the data into its original form. Dividing the data into packets enables the source device to resend only those individual packets that may be lost during transmission.
Private network instances are often used to extend two or more remote customer networks, i.e., private network sites, through a public network, such as the Internet. In some cases, private network instances may be configured to carry multicast traffic, such as Internet Protocol Television (IPTV), desktop conferences, corporate broadcasts, music and video web casts, and other forms of multimedia content. These multicast private network instances include, for example, multicast virtual private local area network service (multicast VPLS) instances, multicast virtual private network (MVPN) instances, and Internet Protocol (IP) multicast instances. In particular, multicast VPLS instances transport layer two (L2) multicast communications, e.g., Ethernet packets, and MVPN instances and IP multicast instances transport layer three (L3) multicast communications, e.g., IP packets, between the customer sites via the public network.
In a typical configuration, provider edge (PE) routers coupled to the customer networks define point-to-multipoint (P2MP) label switched paths (LSPs) within the public network to carry L2 and/or L3 multicast communications as if these customer networks were directly attached to the same private network. In order to discover the private network memberships of PE routers within the public network, each of the PE routers may perform auto-discovery using a routing protocol, such as the border gateway protocol (BGP). After discovering the member PE routes, multicast multi-protocol label switching (MPLS) protocols, including the multicast label distribution protocol (mLDP) and the resource reservation protocol with traffic engineering (RSVP-TE), may then be used to setup P2MP LSPs between the discovered PE routers that belong to the same private network instances.
The need for multicast MPLS is being pushed further to the metro edge of the public network where customer networks are connected together via private network instances. The public network may comprise an autonomous system (AS), which may be logically divided into multiple routing areas, such as interior gateway protocol (IGP) areas. Extending multicast MPLS to these networks comprised of a single AS with multiple routing areas is often referred to as providing seamless MPLS. In the case of seamless MPLS, thousands of PE routers within different routing areas of the same AS require P2MP connectivity to receive multicast communication. The multicast MPLS protocols, however, do not adequately scale to provide multicast communication in this seamless MPLS architecture.